抄録

Sixty-seven strains of pink-pigmented bacteria, which were isolated from environmental water samples collected nationwide, were identified by partial 16S rDNA sequence analysis. In addition, the biofilm formation ability of the isolates was experimentally investigated. We could identify only 2 strains at the species level: <I>Pedobacter roseus</I> HS-38 and <I>Runella slithyformis</I> HS-77. The results showed that of the strains tested, 22 strains (32.8%) were <I>Pedobacter</I> spp., which was most frequently identified, followed by 19 strains (28.4%) of <I>Arcicella</I> spp., 16 strains (23.9%) of <I>Deinococcus</I> spp., 5 strains (7.5%) of <I>Roseomonas</I> spp., 4 strains (6.0%) of <I>Flectobacillus</I> spp. and 1 strain (1.5%) of <I>Runella</I> sp. Most isolates showed low similarity values to previously known species, and they were found to be novel species. At a result, it was difficult to identify environmental water-derived pink-pigmented bacteria at the species level. On the other hand, when we measured the absorbance by the crystal violet staining to examine the quantities of biofilm formation of these strains, fifty-five (82.0%) of the 67 isolates formed biofilm. The absorbance of <I>Deinococcus</I> sp. HS-75 was the highest (3.56). When comparing the absorbance values among the genera, <I>Roseomonas</I> spp. showed the highest absorbance (mean: 1.62), followed by <I>Deinococcus</I> spp.(mean: 1.03), and <I>Arcicella</I> spp.(mean: 1.01). Strains of <I>Flectobacillus</I> spp.(mean: 0.48) and <I>Pedobacter</I> spp.(mean: 0.42) showed lower absorbance values. As above, it was shown that, at the species level, the pink-pigmented bacteria in the water in the Japanese environment had various levels of ability to form biofilm.